engine wont idle once key is let off start

borlax · Aug 28, 2014

Sometimes when I try to start my ranger the only thing it will do is turn over and fire when the key is in the start position. I have to leave it in start to get it to keep firing. Once I let off the key to idle it shuts off. Its getting gas and spark. Maybe the ignition switch? Once in a while I can get it to stay running. Thanks for any help

RonD · Aug 28, 2014

'88 should have the one coil.

The coil gets 12volts when engine is cranking then 8 volts when engine is running, so there are two separate power paths for the coil.

Often on Fords the starter relay will have a 4th post, the "I" post, that connects to the coil and has 12volt only when cranking engine.

There should be another wire on the "+" coil post, it has a ballast resistor that reduces the 13volts(alternator) down to about 8 volts to keep coil from overheating.
This is the circuit you have a problem with.
Yes it could be in the ignition switch or at the ballast resistor.

If you have an ignition Module then Start and Run wires might both be there, and then to coil "+"
Good read here on the Ford TFI system: http://www.therangerstation.com/tech_library/TFI_Diagnostic.shtml

If you run a jumper wire from coil "+" to battery "+" and then start engine it should stay running, this won't hurt the coil short term, so you can drive it this way, but you also should disconnect it so battery doesn't drain

XLTsplash · Aug 28, 2014

I've seen a lot of problems with 80s Ford ignition switches. Many were recalled. They are easy to replace and don't cost much.

tomw · Aug 29, 2014

Take the cover off the steering column by removing the 3 fasteners - philips head screws - from below. Look down the column and see a rod connected from the ignition lock cylinder to the actual switch. Look at the switch. If it is coming apart, you can replace it for ~$10. Take a file and make a straight edge on both sides of both twist-off screws holding stuff together. The twist-offs have no head remaining for a normal wrench to grab, so you have to either drill them out {hateful process} or do my trick. Use an adjustable wrench to remove the screws, disconnect and replace the switch, and replace the screws with normal.
If the engine will stay running by holding the switch just a smidgen towards "start", then the switch is the likely culprit.
tom

borlax · Aug 29, 2014

When I'm cruising in any gear a lot of times it acts like it ran out of gas and then shuts off. It chugs/hesitates. When I try to get it started by revving it high and holding the key in the start position it has backfired a few times when I let off the clutch in first. I have the H.E.I ignition and a weber 2 barrel. Is the ignition still the likely problem? Thanks for the answers, I will be checking this out today.

alfacliff · Aug 29, 2014

sounds like the ignition coil ballast resistor has gone bad.
My old 88 had a problem with igntion, the distributor cap was bad and the ht wire from the coil to the distributor cap was also bad. started it u one night with the hood open, and lots of sparks crawling all over the high voltage lead from the coil to the distributor.

borlax · Aug 29, 2014

Where is the ballast resistor? This truck had a Duraspark ignition stock. Could it be the HEI ignition module? I also don't know where the switch is that the ignition lock cylinder goes to, I didn't see a rod after removing the steering column cover.

tomw · Aug 30, 2014

Look at the column and see what the key moves when moved from ON to START. Mine has a rod that goes down the column and moves the gizzards of a sliding switch. Mine was 'expanding' because the wire loom connected was stressed and pulling the switch apart for 20+ years, and the little pot metal 'ears' were letting it come apart. IOW, look closer.

Will the engine stay running if you push the key just a smidge towards START?

tom

RonD · Sep 2, 2014

borlax said:
Where is the ballast resistor? This truck had a Duraspark ignition stock. Could it be the HEI ignition module? I also don't know where the switch is that the ignition lock cylinder goes to, I didn't see a rod after removing the steering column cover.

GM style HEI won't need a ballast resistor, but your old wiring might have one somewhere.

Could still be ignition switch cutting 12v to HEI intermitantly.
12 volt power comes from ignition switch to Coil "+" and "B" on HEI module, intermittent connection on either would cause stall(no spark), so check those connection first.

Ignition switch is under the steering column.

engine wont idle once key is let off start

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